In recent years, a driving support system that displays an image of a virtual vehicle at a position between a tail of a traffic congestion and a subject vehicle that is approaching the tail of the congestion has been developed. The system displays the vehicle image on a transparent glass, i.e., on a windshield, for the driver of the subject vehicle. The system having this kind of driving support scheme is disclosed in, for example, Japanese patent documents JP-A-2002-144913 and JP-A-2005-127996.
However, an image position of the virtual vehicle projected on the windshield sometimes overlaps a look direction of the driver who watches a real leading vehicle at the tail of the congestion. In this case, the image of the virtual vehicle obstacles the driver's sight, and thus causes a trouble for recognizing the existence and the position of the real vehicle ahead of the subject vehicle.
Further, Japanese patent document JP-A-2005-127996 describes in the disclosure that the system changes the image position or an image type of the virtual vehicle depending on the existence of the real leading vehicle. However, turning on and off of the image of the virtual vehicle depending on the existence of the real leading vehicle may throw the driver of the subject vehicle into confusion contrary to an intended effect of the system.